Abstract
As and Cd in soil can be assimilated and accumulated by vegetables and can be subsequently ingested by humans. Contradictory effects of organic fertilizer application on As and Cd accumulation in soil have been reported in previous studies. An eight-year greenhouse study was conducted on a sandy loam soil in Beijing, China to investigate the effects of organic fertilizer application rate on soil properties, and As and Cd accumulation in soil. The contamination risk of pak choi grown after eight years’ application of organic fertilizer was also evaluated. Soil organic carbon increased 3.0–3.8 times with low, medium and high rates of fertilizer application in 2018 compared to the initial soil. Organic fertilizer application significantly increased soil nutrients and microbial biomass while it mildly affected soil pH. The bioavailability of As/Cd has decreased after eight years’ application of organic fertilizer. Pak choi crop harvested from all three treatments in 2018 did not pose a threat to human health, even for life-time consumption. Soil total As content significantly decreased with organic fertilizer application, mainly due to the lower As content in the applied fertilizer than that in soil. Continuous application of clean organic fertilizer can be adopted to reduce the contamination risk of highly contaminated soil in the soil–plant system.
Highlights
Trace element contamination in soil poses a threat to food safety and public health.According to the first Chinese national soil pollution survey conducted from 2005 to 2013, approximately 26 million ha of arable land in China was contaminated with trace elements, with Arsenic (As) and Cadmium (Cd) being the principal contaminants in 2.7% and 7.0%of arable land, respectively [1,2]
The objectives of this study were to (1) clarify the effects of long-term organic fertilizer application on soil properties, such pH, organic carbon (C), soil nutrient supply and microbial biomass, As and Cd bioavailability and accumulation in soil; (2) evaluate the health risk of pak choi grown on these soils; and (3) determine the key factor on whether As and Cd contents increase or decrease with organic fertilizer application in the soil–crop system
Based on the conclusion from this study that soil trace element contents can be decreased by continuous application of clean organic fertilizer with low trace elements contents, we propose the application of clean organic fertilizer to lower the contamination risk of soil with high As and Cd levels
Summary
Trace element contamination in soil poses a threat to food safety and public health.According to the first Chinese national soil pollution survey conducted from 2005 to 2013, approximately 26 million ha of arable land in China was contaminated with trace elements, with Arsenic (As) and Cadmium (Cd) being the principal contaminants in 2.7% and 7.0%of arable land, respectively [1,2]. Based on the data from 548 soil samples, the average As and Cd contents were 6.48 and 0.13 mg kg−1 in facility vegetable production nation-wide, with 1.6 and 5.3% of the area being contaminated with As and Cd, respectively [3]. High As and Cd contents were reported in 162 commercial organic fertilizers where total As contents ranged from 0 to 14.1 mg kg−1 and total Cd contents ranged from 2.0 to 256.0 mg kg−1 [4]. Huang et al [6] analyzed 126 commercial organic fertilizers and reported average As and Cd contents of 5.6 mg kg−1 (range, 0–23.3 mg kg−1 ) and 1.2 mg kg−1 (range, 0.1–5.3 mg kg−1 ), respectively
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